Wireless signaling system



E; F. w. AL EXANDERSON.

WIRELESS SIGNALING SYSTEM. APPLICATION FILED rfpv. 26. 1911. PatentedAug. 12,1919.

Inventor: Ernst F. WDHe-xanderson,

His Dfttqrheg UNITED. STATES PATENT cur os;

ERNST F. W. ALEXANDEBSON, 01E SCHENECTA DY, NIEW YORK, ASSIG'NOR "1'0 ELECTRIC COMPANY, A CORPORATION-OF NEW YORK.

wmELEss SIGNALING SYSTEM.

Specification oI Lctters a. Patented Aug. 12, 1919.

Application filed November 26, 1917. Serial No. 203,915.

To all whom it may concern:

Be it known that 1, ERNST F. W. ALEX- ANDERSON, a citizen, of the United States,

residing at Schenectady, in the'county of Schenectady, State'of New York, have invented certain new and useful Improvements in Wireless Signaling Systems, of

. which the following is a specification.

My present invention; relates to w reless In carrying my-invention into effect I employ separateantennze for transmitting and receiving purposes. Both of these antenna: may be suspended from the same towers in whole or in part, or maybe located in fairly close proximity to each other upon separate towers. In order to overcome the effect in the receiving apparatus of the waves impressed upon the receiving antenna from the transmitting antenna, I derive from the transmitting antenna, an electromotive force equal in value and opposite in direction to the potential induced upon the receiving antenna from the transmitting hntenna and impress this electromotive force upon the receiving circuit in such a manner as to neutralize in the receiving aparatus the effect of the induced potential.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however. both as to particular embodiments thereof and mode of operation, will be best understood by reference to the following description taken in connection with the accompanying drawing in which Figures 1 and 2 show two modifications of my invention, and Fig. 3 is a diagram explanatory of the form shown in Fig, 2.

In Fig. 1, I have indicated a transmitting antenna 1 supported upon towers 2 and 3.

A receiving antenna 4 which is insulated from the transmitting antenna is supported upontowers 3 and 5. The receiving antenna 'tenna may its may be supported upon the towers 2 and 3.

or may be supported inde endently of eitherof these towers but -in c ose enough proximity to-the-transmitting antennaso that both antennae my be readily connected to the operatin station. The transmitting ane su plied with signaling current from a high frequency alternator 6 coupled thereto by means of the coils 7 and 8. The tuning of this'antenna may be accomplished by means of the usualvariable inductance 9. The receiving antenna at is 4 connected to earth at 10' through the coil 11 which is coupled to the coil 12 in the receiving circuit of the electron discharge device 13 which may serve as an amplifier and de tector for the signals which it; is desired to receive. The receiving circuit comprises the cathode l i of the device, thegrid 1'5 and a variable condenser 16 for tuning the circuit to the frequency of the waves to be received. The detector circuit of the device comprises the cathode 1a, anode 17, a battery 18 for supplying the operating current, and the usual telephone receivers 19, these receivers being shunted by the condenser 20 which serves to by-pass the high frequency component of the current flowing in the circuit.

With the system thus far described, when signals are being transmitted potentials of such magnitude willbe induced in the receiving antenna that the received signals will be unintelligible even though the two sets ofsigna-l's maydifier considerably in frequency. To overcome thisdiiiiculty I provide a shunt connection to the transmitting antenna from the point 21 to earth at 22 through the inductance 23. The inductance 24 is coupled to inductance 23 in such-a way that the potential induced therein is equal and opposite to that induced from trans-.

mittingantenna 1 upon receiving antenna 4. The potential thus obtained is impressed upon the receiving antenna by means of the connectin wire 25, a variable condenser 26 being included in the circu-it for tuning it to the frequency of the transmittingcurrent. The two opposing potentials thus neutralize each other and as a result the receiving apparatus will not be afiected by the-waves transmitted, from antenna 1. culty is experienced in adjusting the neu- If anyditlitralizing circuit in such a way as to entirely a frequency trap consisting of a condenser 27 and inductance 28 may be inserted in the overcome the efiectcf the transmitted waves receiving circuit. If this frequency trap is tuned to the frequency of the waves transmitted it will offer a high impedance to waves of thatfrequencyand a much lower impedance to received waves which differ somewhat in frequency from the waves transmitted. I have indicated as a means for controlling the current in the antenna a switch 29. It will, of course, be understood, however, the antenna current may be controlled in any desired way for transmitting either telegraphic or telephonic signals.

In the form of my invention shown in Fig. 2 the main neutralization of the induced p0 tentials in the receiving antenna is accomplished by an arrangement of electrostatic condensers with an additional electromag netic coupling for obtaining a'final adjustment of the system. The neutralization effeet in this case is to the highest possible degree independent of the frequency and,

therefore, a higher degree of neutralization is possible." The neutralization is also substantially independent of fluctuations in the operation of the transmitting apparatus and the regulationof the system is simple. The operation of this system is based upon the lVheatstone bridge principle and will be best understood by reference to the diagram of Fig. 3.0 In this diagram the condenser i ture and the counterpoise condenser has a fixed capacity which is not changed during the operation of the system. The third arm of the bridge which I term theitexposure capacity of the receiving aerial comprises the natural capacity between the transmit ting and receiving antenna: and is represented by the condenser 32. This capacity also';--"is determined by the antenna structure and is substantially constant. To balance this exposure capacity I employ a condenser 33 which I term the exposure capacity of the counterpoise. The condenser 33 may be of such a value as to balance the system so thatthe points 34 and 35 at the ends of the receiving coil 11 are at Substantially equal potentials in so far as the transmitted waves are concerned. In this arrangement the potential across the capacity 32 represents the induced potential on'the receiving antenna and-the potential across condenser 33 is a potential derived directly from the ing systems.

transmitting antenna whichis connected to the receiving coil 11 in such away as to neutralize therein, the fi'ect ofthe potential.

across capacity 32.

When the electrostatici balancewhich I have described is employed, Ihave found that it is desirable that the receiying set should be screened from theetfectfof any electrostatic field which. may be-produced in the receiving coil 11. In order t0 accom plish this purpose I have indicated iniFig.

2 a metallic shield 36 surrounding the coil- '11, this shield being grounded and split vertically in such away as to prevent the short circuiting of the ma etic lines a of force.

The switch 37 for ad uSting-the inductance of coil llis' also inclosed within this shielding member 36. In this case instead'of; coupling the coil 11 directly to the coil 12 I may employ an intermediatecoupling circuit com-prising a; coil 38, of a few turns wound around the shield 36 and a second coil 39 in circuit with coil 38 and which-is coupled to the coil 12. f

In actual practice it may be found desirable to proportion the condensers 31and 33 so as to bring the system to an approximate balance; The final balancing adjustment use of an additional electromagnetic coupling between the transmitting andreceiv- As here shown a potential is derived from the transmitting system by the coil 40 which is coupled to coil 8. The potential obtained may then be very conveniently made'by the I I have indicated in Fig. 2 the manner in which this may be brought about. i

by means of this coil is applied to the grid circuit of detector 13-by means, of coil 41 which is coupled to the coil 12, the coupling between these two coils being adjustable so that by varying this coupling the desired balance'between the systems may be effected. It will be noted that in the arrangement shown in Fig. l the electromagnetic coupling is made to the primary of the receiv ing set. It may be found in practice that the receiving apparatus will be influenced by strays other than those received directly;

on the antenna. If this is the case, these strays will not vary in intensity in the same manner as the transmitted signals'andin.

order to maintain a balance in the system frequent adjustment-may be necessary; It'-- will be found that less adjustment will berequired and thatthe adjustment may be. made more easily and conveniently if theelectromagnetic coupling is applied to the secondary of the receiving set as indicated in Fig. 2, as in this arrangement theconipensating electromotiveforces do nothave to pass through the transformation between primary and secondary of'the sys- 1 tem but are applied directly to the art ofthe circuit where their effect is desi this reason, in case the electromagie cou- For pling alone is used for compensation it may two modifications of my invention, it will be apparent that many variations in the circuit arrangements used and the form of apparatus employed maybe made without departing from thescope of my invention as set forth in the appended claims.

\Vhat I claim as new and desire to secure by Letters Patent of the United. States, is: 1.,The combination in a wireless signaling system of a receiving antenna, a sepa rate transmitting antenna in proximity thereto, and a receiving system comprising a receiving coil having one end connected to said receiving antenna and its opposite end connected to a point between two capacities, one of which is connected to earth and the other. ot which is connected to the transmitting antenna, and an electromagnetic coupling between the transmitting antenna system and the receiving system.

2. Thecombination in a Wireless signaling system of a receiving antenna, a separate transmitting antenna in proximity thereto, a receiving system comprisinga receiving coil having one end connected to said receiving antenna and its opposite end connected to a point between two capac1ties,-

one of which is connected toearth and the other of which is connected to the transmitting antenna, the two capacities being so proportioned with respect to the. capacity of the receiving antenna and-the mutual capacity between the antennae, that the two ends of the coil are at substantially equal potentials with respect to the transmitted waves, and an electromagnetic coupling be tween the transmitting antenna system and the receiving system.

3. The combination in a. wireless signaling system of a receiving antenna, a separate transmitting antenna in proximity thereto, areceiving system comprising a receiving coil having one end connected to the receiv mg antenna and its other end connected to a point which is of substantially equal potential, with respect to the transmitted waves, and an electromagnetic coupling between the transmitting antenna system and the receiving system.

:l'. The combination in a wireless signaling system of a receiving antenna system comprising primary and secondary circuits, a separate transmitting antenna in proximity thereto, the primary circuit of said receiving system comprising a receiving coi'l having one end connected to the receiving antenna and its opposite end connected to a point between two capacities, one of which isconnected to earth and the other of which is connected to the transmitting antenna and.

an electromagnetic coupling between the transmitti n g antenna system and the second ary circuit of the receiving system.

5. The combination in a wireless signaling system of a receiving antenna system comprising primary and secondary circuits, :1. separate transmitting antenna in proximity thereto, the primary circuit of said receiving system comprisin a receiving coilhaving one end connecte to the receiving antenna and its opposite end connected to a. po1ntbe= tween-two capacities one of which is connected to earth and the other of which is connected to the transmitting antenna, the two capacities being so proportioned with respect to the capacity of the receiving antenna and the mutual capacity between the antennae that the two ends of the coil are at substantially equal potentials with respect to the transmitted waves, and an electromagnetic coupling between the transmitting antenna system and the secondary circuitof the receiving system.

6. The combination in a wireless signaling system of a receiving antenna system comprising primary and secondary circuits, a separate transmitting antenna in proximity thereto, the primary circuit of said receiving system comprising a receiving coil having one end connected to the receiving antenna and its other end connected to a point. which ishf substantially equal potential with respect to the transmitted waves and an electromag netic coupling between the transmitting antenna system and the secondary circuit of the receiving system.

7. The combination in a wirelem signaling system of a receiving antenna system comprising primary and secondary circuits, a separate transmitting antenna system. in proximity thereto, the primary circuit of said receiving system comprising a. receiving coil having one end connected to the receivin antenna and its other end connected to a point which is at substantially equal potential with respect to the transmitted waves and an electromagnetic coupling between a source of radiations and the secondary circuit of said receiving system whereby electroirnlotive forces may be impressed upon the receiving system which are opposite in directions to the electromotive-forces produced therein by radiation from the transmitting antenna system.

In witness whereof I have hereunto set my hand-this 23rd day of November, 1917.

ERNST'F. wv. ALEXaNnnRsoN. 

